interpreter : Java Glossary

An interpreter is a computer program that makes a real cpu, such as an Intel Pentium,
simulate the idealised Java CPU (Central Processing Unit). An interpreter does not
convert the JVM (Java Virtual Machine) byte codes to machine code. It runs the
JVM byte codes
directly, using a program to simulate, in every detail, exactly what an idealised
Java CPU would do.
There are cpus that can run JVM byte codes directly as their native machine code. When
you use these, that is not called interpreting. It is only called interpreting when
you use a program to make one computer pretend to be another.

Interpreter is also one of the design
patterns. It has nothing to do with interpreting JVM
byte codes.